It appears that schizophrenia and epilepsy are linked in both directions. Researchers in Taiwan confirmed the link when they found study participants with epilepsy were nearly 8 times more likely to develop schizophrenia, and those with schizophrenia were nearly 6 times more likely to develop epilepsy. A paper on their work is due to be published today in Epilepsia, a journal of the International League Against Epilepsy (ILAE).

Previous studies have suggested that psychosis is more prevalent among people diagnosed with epilepsy, and there appears to be a strong link between schizophrenia and epilepsy. Greater susceptibility to both illnesses could be due to similar or shared genetic, environmental or neurobiological causes.

But, while several studies have shown links between between depression, mood disorders and epilepsy work in both directions, this is thought to be the first to look at schizophrenia and epilepsy in this way.

For their study, lead author Dr I-Ching Chou, who is based at China Medical University Hospital and is also Associate Professor at China Medical University in Taichung, Taiwan, and colleagues, examined records from the Taiwan National Health Insurance database. They found data on 5,195 patients with schizophrenia and 11,527 patients with epilepsy, diagnosed between 1999 and 2008.

After matching both cohorts to controls free of either illness for age and sex, they analyzed the incidence and risk of the schizophrenia group developing epilepsy, and of the epilepsy group developing schizophrenia.

The results show that:

  • The schizophrenia group had a higher rate of epilepsy than the controls (6.99 compared to 1.19 per 1,000 person-years respectively) and were nearly 8 times more likely to develop schizophrenia.

  • Similarly, the epilepsy group had a higher rate of schizophrenia than the controls (3.53 compared to 0.46 per 1,000 person-years respectively) and were nearly 6 times more likely to develop epilepsy.

  • There was a slightly higher rate of schizophrenia in men with epilepsy than in women with epilepsy.

The researchers concluded that their findings show a strong bidirectional relation between schizophrenia and epilepsy.

“This relationship may be due to common pathogenesis in these diseases such as genetic susceptibility and environmental factors, but further investigation of the pathological mechanisms are needed,” said Chou.

Written by Catharine Paddock PhD